When a system, whether a monoprocessor or a multiprocessor, is booted, the core or operating system typically functions in a physical addressing mode, also called the real mode, as long as the memory management unit thereof is not initialized. As soon as the memory management unit is initialized, the core of operating system operates in a virtual addressing mode, and only then can a debugging tool, which generally functions in the virtual mode, become operational. This has a certain number of disadvantages. The initializing phases cannot in fact be debugged until after initialization of the memory management unit, since the debugging tool or "debugger" that uses the virtual addresses is dependent on the memory management unit, which translates the physical addresses into virtual addresses. Accordingly, an error occurring during the initialization phases can be difficult to detect; and result in the system remaining blocked. Similarly, because the debugging tool depends on the memory management unit, a change from the current context to some other desired context cannot be authorized in a simple manner, since only one context is valid at a given moment through the memory management unit. Finally, when a failure in virtual memory occurs, either during the initialization phases, when the debugging tool is not yet active, or later when the virtual memory is initialized, this tool can be perturbed considerably, since it uses the same virtual memory; moreover, under these conditions, it cannot be used to analyze such failures.